This invention relates to supporting a 2-piece container on a mandrel during a beading operation and, in particular, to a technique which assures the axial position of the container relative to the beading tool. Two-piece containers for packing comestibles are currently of interest in connection with replacement of the 3-piece sanitary food containers which were the standard of the industry for packaging foods. Three-piece containers are formed from a flat blank of sheet which is rolled and seamed along a longitudinal side by bonding, welding or soldering. The hollow cylindrical tube thus formed is capped at one end with an end closure by the manufacturer of the container. The end closure is held to the container by a hermetic double seam of interfolded metal along the periphery of the end closure and the hollow tubular cylinder.
It is common to precoat the blank before forming with plating or an organic coating to protect the food which is ultimately to be packed within the container from the harmful effects of the container or vice versa. With a 3-piece container a postcoating and/or side seam stripe is required to cover the areas damaged during manufacture by the body maker (which rolled the blank) or the side seaming processing.
In contrast, 2-piece containers are formed from precoated plate which is drawn into a cup-shape and if need be redrawn into a taller and narrower cup. Such drawn containers eliminate the need for forming or repairing side seams and overcome the concern about the quality or integrity of the double seamed bottom. That is to say that, the two pieces of the 2-piece container are the drawn container or cup and the end closure which the packer double seams hermetically to the top of the container after the comestibles are packed. No post or repair coatings are necessary for drawn containers. Precoats have been found which form adequately in connection with the drawing operation and yet maintain their integrity even after the converting of a flat sheet of precoated metal into an elongated cup-shape.
Most containers for packing comestibles are subject to processing conditions resulting from hot filling and/or retort processing. More specifically, hot food stuff is added to the container and the container is sealed. Upon cooling the internal pressure of the sealed container is less than the external atmospheric pressure. The pressure differential causes stress in the side walls of the hollow cylindrical container which must be adequately resisted by the strength of the container. Similarly, foods which are packed in a container which is then sealed and heated in a steam retort tend to expand during heating and then to shrink in volume during cooling. The later causes a lower internal pressure which results in even greater stress than those resulting from hot filling because the extremes are greater.
Should the filled and processed container be inadequate to resist the pressure differential, the side walls of the container will collapse inwardly forming panels which indicate the can has inadequate hoop stress resistance. One solution to this strength problem is to make the container of heavier gauge and harder or stronger materials. This solution is a problem in that the cost of the container and the difficulty of making same is increased. Another approach which has been used with great success has been to add a series of concentrically disposed side wall beads or corrugations which act to enhance the resistance to panelling. Beads are applied by certain techniques and can be used with either 2-piece or 3-piece containers.
One technique for applying beads to the side wall of a container is a system sold by REDICON, H & H Industries Inc., Dayton, Ohio, being a 12 Spindle Rotary Beader. This machine has a series of mandrels which support the drawn container and roll same across a fixed beading rail having grooves which match complimentary beading ribs disposed about the outer periphery of the mandrel. The mandrel has a smaller outer diameter than that of the interior diameter of the container and consequently when positioned within the container the axial center line of the mandrel is eccentric with respect to the axial center line of the container. When the mandrel and container carried thereon are rolled across the fixed beading rail the mandrel presses the container such that beads are formed between the ribs on the mandrel and the grooves on the rail.
Two or three-piece containers may have their beads placed specifically to generate a predetermined resistance to panelling. Even so, the specific location of the bead relative to the side wall varies somewhat from container to container. That is to say that, the position of the container relative to the mandrel will vary as a result of the shrinkage in overall can height due to beading and can height tolerances resulting from manufacturing. There are guide rails disposed normal to the axes of the mandrel and the container. These surfaces guide and align the container on to the mandrel before the container is brought into contact position against the beading rail.
Two-piece containers have a certain criticality with respect to where the beading is placed because the 2-piece containers include bottom chime-like beads which must be positioned at a predetermined axial relationship relative to the bottom of the container. More particularly, the beading mandrel used for 2-piece containers includes a bottom beader which is positioned at the most distal peripheral portion of the mandrel to cooperate with a similarly positioned groove on the fixed beading rail for generating a chime-like bottom bead. The chime-like bead is placed on each container so that it will be fully interchangeable with the 3-piece container which it seeks to replace. As already mentioned, the 3-piece container includes a double seamed bottom closure which is put on during the manufacture of the container. The double seamed bottom includes a double seam chime that gives the 3-piece container an outwardly extending circumferential lower periphery. Years of packaging and processing such containers have caused the industry to invest in equipment designed to handle such containers with the top and bottom peripheral double seam extensions. More particularly, the containers after packing and closure with a hermetically double seamed top are able to roll along can conveyors, during retort processes and into labelling equipment. Thus, the trackwork is adapted to cooperate with the chime surfaces of the double seams (top and bottom). It is a fact that such trackwork develops grooves as a result of the number of containers that have passed therethrough.
The 2-piece container therefore must have an accurately located chime-like lower bead to replace the missing chime of the double seamed bottom closure. More particularly, the bead has to extend from the outer diameter of the container body side seam the same amount as would a double seamed chime and the longitudinal length of the bead should be equivalent of that of a double seamed chime. In order to have complete interchangeability a 2-piece container must support a label between the chime-like bead and the upper double seam in a manner identical to that which occurs in connection with a 3-piece container where the label rests between the upper and lower double seams.
It has been found that the tolerances between the backup rail and the mandrel flange of a conventional beader used for beading 3-piece containers, were troublesome with regard to 2-piece containers in that the bottom of the container was not positioned relative to the bottom beader portion of the mandrel. More specifically, the location of the chime-like bead was found to vary relative to its position with respect to the 2-piece container bottom. The present disclosure seeks to assure the positioning of the bottom chime-like bead by controlling the position of the 2-piece container relative to the beading mandrel.
Prior patent art discloses techniques for holding containers relative to the tools which are used for forming them. The McDonald U.S. Pat. No. 648,280 shows a combined beader and flanger having no specific system for precisely locating the beading relative to the side wall of the container. Similarly, the early patents to Lotz U.S. Pat. No. 632,840 and Coyle U.S. Pat. No. 1,912,258 disclose collapsible mandrels used for supporting the container during flanging, but fail to show any specific means for accurately axially positioning the container relative to the beading tool. Several arrangements are known for supporting containers of varying heights during double seaming or necking and flanging, see Black U.S. Pat. No. 858,785, Heinle U.S. Pat. No. 3,771,476 and Heinle U.S. Pat. No. 3,757,558 which disclose techniques for supporting the container bodies. These references are of interest to the improvement of the present disclosure but are inappropriate to the specific problem and the particular solution herein disclosed.